Lionheart timeline
A ransom of the King
The emperor probably agreed with King Philip, already in conflict with the English king, on Richard's capture. When Richard left the Holy Land in late October 1192, he found the French ports closed and sailed up the Adriatic Sea. He took the country road from Aquileia across Austria, to reach the Bavarian estates of his Welf brother-in-law Henry the Lion. Whilst travelling under disguise, he stopped at Vienna shortly before Christmas 1192, where he was recognized (supposedly because of his signet ring) and arrested in Erdberg (modern Landstraße district). Initially Duke Leopold V had the king imprisoned in Dürnstein, and in March 1193 Richard was brought before Emperor Henry VI at Trifels Castle, accused of Conrad's murder. A ransom of 35,000 kilograms of silver was paid to release King Richard. Leopold demanded that Richard's niece, Eleanor, marry his son Frederick. Due to Leopold's death, this marriage never took place. Leopold's share of the ransom became the foundation for the mint in Vienna, and was used to build new city walls for Vienna, as well as to found the towns of Wiener Neustadt and Friedberg in Styria. The duke was excommunicated by Pope Celestine III for having taken a fellow crusader prisoner.
To receive absolution, Leopold V prepared for another crusade and decided to improve his relation with the Church by improving his relations with the clergy, when Eleanor of Brittany arrived with Baldwin of Bethune she was welcomed by Duke Leopold V in open arms and he himself prepared to embark on a new crusade, she married Frederick on 1197.
The marriage between Eleanor and Frederick would have produced two daughters, Helena(1199) and Constance(1209) and two sons, Frederick(1202) and Heinrich(1207).
Note: the Eldest son of Frederick II will naturally marry Constance, the Grand-Niece of Richard I not Agnes as OTL.