Yukino has always been alone on things, it wasn't that he was poor but the fact he didn't have anyone to help him or take care of him really hurt him. He has 5 kids who love him, he all adopted them to show them that not all rich people in the world are neglecting abusers who can't think straight.
And looking after exotic animals he rescued surely wasn't enough, he barely had time for himself!
So the siblings decided that their mommy needs to have a sugar daddy.
[Diabolic lovers crossover-That time I got reincarnated as a slime- Tokyo ghoul- Fairy tail- The rising of the shield hero- messenger bird-]