Well, given that the parents in the 1911 census are Andrius and Katorina, and Andrius and something like Kate on Palonia's birth certificate, and that the maiden surname of Palonia's mother is Jablonskutie and the maiden name of Andrius' wife is Katrina Yablonskiute, I reckon that is indeed Juozas' little sister. (I assume that the 1911 census says that Palonia was born in Scotland?) I wouldn't worry too much about the -wicz- bit in the middle, which is the Slavonic equivalent of 'Mac' in a Scottish name.