Indeed, the Basileus had returned to Constantinople, two months previously, for the second time mid-campaign, in anticipation of the arrival of another Crusader army, this one comprising Hungarians, Serbians and Croatians. Their leaders were
Justiciar George [Hungarian: Cronik fia György],
Macarius, Archbishop of Esztergom [Hungarian: Makár], and the Serbian prince
Zavida, Župan of Zachumlia.
Oh boy, they managed to drag Zavida into their party! By this point, all his boys had been born as per OTL (Nemanja, his youngest, born in 1113), so there's no worry about them somehow getting wiped, but I do wonder have to wonder about ol' Zavida himself, so the remainder of this post is going to be some impromptu research.
I haven't really seen many decisive comments on when ol' Zavida actually died (or heck, who his parents are) - the English Wikipedia article mentions not a thing, while the Serbian article mentions the various assumptions made on the father department (Ljubomir Kovačević in 1900 and Tibor Živković in 2006 thinking his father is Vukan, Stanoje Stanojević thinking it was Vukan's son, Stefan Vukan, and Jan Lesni thinking it is Uroš I Vukanović), whilst leaning more towards Živković's interpretation (which puts Zavida's death after 1127, linking him with an unnamed-yet-imprisoned Rascian prince, more on that in a bit).
Speaking on Zavida, while we know not who his father was, following the death of Vukan, there was an apparent power struggle between the Vukanovići, which would, among other things, ultimately result in Zavida being exiled from Zachumlia to Doclea, where, in Ribnica (of which he'd become a Lord of), Nemanja would be born. By Živković's interpretation, Zavida, in his belief being one of Vukan's sons, was supposed to be the successor, but the involvement of his brother Marko would see Uroš I, his own son, come to power instead (Stanoje's interpretation would make Zavida Uroš's cousin). Uroš I would closely collaborate with Đorđe Bodinović, who would even go into hiding under his rule after being defeated by the Byzantines, who conquered Doclea and enthroned Grubeša Branislavljević. From there, Đorđe would reinvade Doclea with Uroš's help, killing Grubeša without the Byzantines reacting due to their being busy in the east. Gradihna Branislavljević, Grubeša's brother (and both were Đorđe's cousins?), would end up possibly subverting Uroš' rule and linking up with Zavida's daughter (or maybe he just moved to Rascia to avoid Cousin Đorđe, and just married Zavida's daughter for less subversive reasons). In the meanwhile, Đorđe would give his other two cousins, Dragihna and Dragil, Zeta, where Zavida was supposed to still be.
However, circa 1123/25, there is an assumed change of power, by an unknown individual. Živković, based on some vague-ass wording from the Hagiography of St. Simeon and the fact that John II Komnenos countered a Pecheneg invasion into Paristrion in 1122/3, concludes that the Byzantines sent a small force to assist Zavida, who's pro-Byzantine, in coming to power in Serbia once more. And then during the 1127-1129 Byzantine-Hungarian War, after the invasion of Serbia, according to the Gesta Hungarorum, the Hungarian army imprisoned and took with them an unnamed Rascian prince. With the assumption of Zavida having come back to power, Živković once more concludes that said prince was Zavida. With this in mind, at this point, Đorđe found out that Uroš had been imprisoned, and as such, overthrew whoever was left in power in Serbia (likely Zavida's four sons) and reinstated Uroš, who would then unfortunately become a Byzantine vassal. Uroš would later then assist the Byzantines in overthrowing Đorđe in 1131, who gets imprisoned in Constantinople, where he dies. Meanwhile, Zavida ended up dying in Hungarian captivity, while Uroš would rule until about 1144/5, and Gradihna came to power in Doclea.
Now, the big question becomes this - should we consider Živković's interpretation to be the correct one here? Admittedly, having Zavida here would be more entertaining, as one could argue against his interpretation and keep him alive in Zeta (and it is said that Nemanja became of age while in Rascia, indicating that Zavida's family did return at some point in the mid-12th century [at earliest the 1130s, at latest the 1150s], likely after at minimum Đorđe was overthrown) even if he likely wouldn't be Župan of Zachumlia as a result of Uroš I still being in power (and Desa Vukanović seeming to rule Zachumlia before becoming the sole ruler of Serbia himself after co-ruler Uroš II). Alternatively, having Desa, the youngest of Uroš's sons, represent the Vukanovići might be more appropriate instead, as apparently, according to Croatian sources, he was "rather compliant to Catholic law" and had apparently built a monastery dedicated to the Virgin Mary on the island of Mljet during his reign as ruler of Zachumlia (of course, those very same sources seem to claim that Nemanja was Desa's son, so how accurate it is, I know not). And besides, at this time, Zavida is likely still pro-Byzantine, and possibly may not have joined a crusade organized by the Hungarians.
And as an aside, Uroš II and Beloš, who was Uroš I's middle son, had close ties and counted on one another, such as in 1149, when the latter's Hungarian army aided the former against the Byzantines. Meanwhile, Desa would be Prince of Doclea (after defeating Radoslav of Duklja), Travunia and Zachumlia. Basically, both the brothers didn't really have a good relationship with the Byzantines. After they got their asses beat, Uroš II swore his loyalty and tried to throw Desa under the bus, but he swore loyalty too, and thusly the two were made co-rulers, splitting Serbia internally in two. But the two still couldn't get along, so Desa, while the Byzantines were busy with other things such as the Hungarians, deposed his brother following a dispute in 1153 with the help of the pro-Hungarian faction at the court. Uroš II would be restored in 1155, after Manuel I settled the dispute between the two, deposing Desa and giving him an appanage of Dendra near Niš (which may be known as Dubočica in Serbian, or Dubrava, scholars aren't exactly sure), leading to the growing unfriendliness between Desa and Manuel. And then, in the lead-up to Manuel I attacking Hungary, Manuel ended up deposing Uroš II in 1162/3, moving him to a nice little estate where he couldn't be a threat to his interests, though it is assumed he died not too long after getting deposed. Beloš ended up briefly coming to power in Serbia, before just giving it to Desa and returning to Hungary. Desa's unfriendliness with Manuel would culminate with him refusing to return Dendra, leading to accusations of him trying something with the Hungarians. Some shit happened here in regards to that, and it led to his ass getting beat by the Byzantines in 1165 at Niš. And from there, he decided to put Zavida's sons into power, splitting Serbia internally by four while naming one of them the Grand Prince - Tihomir Zavidović, the eldest, was the Grand Prince and Prince of Rascia; Miroslav was Prince of Zahumlia (and Travunia, it appears); Stracimir was Prince of the territories of the West Morava; and the youngest, Nemanja, was Prince of Toplica, Ibar, Rasina and (Puste?) Reke.
I won't mention Helena's eager sponsoring of the Hungarian Crusade, mainly because I'm unfamiliar with her relationship with Catholicism, so that I'm willing to accept. The only other of Uroš I's kids I haven't mentioned in this post yet is Marija Vukanović, who married Conrad II Přemyslid of Znojmo.
...I wonder what Boris Kalamanos is doing right about now.
EDIT: Watch this, this post will metamorphose in the blink of an eye, including
even more info!