Completely frustrated

Just needed to vent and this is the only where I could think of. My fiancé and I have been together for 4 years we have been trying for a baby for 2 years and this coming year planned on buying a house and paying off our cars. For Christmas he went to see his family while I stayed home due to all the Covid stuff. My fiancé saw my sister in laws 2 oldest kids and the youngest. She left to go visit the youngest in another country which she had money to do. The oldest 2 (12) (7) had ripped cloths and shoes too small so he took them to get new shoes and cloths. He saw the youngest 1 who is 6 months old who his sister left with his other sisters mother in law. She sent her 2 middle kids (6)(5) to live with family in Mexico. We were frustrated that she wasn’t taking care of the kids but left it and just tried to enjoy Christmas. Today she said she wants to “barrow” $4,000 to help the youngest father move from where he’s living now. I told my fiancé I wanted to talk about it tonight since last time we gave his dad $1500 to move we lost a bunch of money. I’m just frustrated that my fiancé has put in so much overtime and I have worked hard to be able to have money saved so we can do the things we want to do like buy a house but his family just sees just as a piggy bank.