Richeza of Poland's son (Fernando (b.1153)) by Alfonso VIII of Castile survives. Not sure how he could become duke of Galicia in eastern Europe, maybe through advantageous marriages or conquest. Then, he/his line ends up as High Duke (later king) of Galicia (Poland). A daughter marries the crown prince of Castile (who happens to be styled duke of Galicia), while her brother is murdered/dies while out hunting/killed in battle/insert reason here. Bam, Galicia and Galicia united.
The other situation involves Wladyslaw III abdicating after Varna, taking the style of duke of Galicia and heading to Reconquista Iberia where he carves out a fiefdom of Galicia for himself.
Both crazy. Probably ASB but there you go