He helped the orphans because in the first place, He love those orphans unconditionally. And second is, there's no any other relatives of the orphans who can help them. He played as an uncle and at the same time as a father also. And that is a good image to all uncles out there.
Because they were orphans and they didnt have any other family or a place to go. since he was older than them and fatherly figure to them, who took them in, love them, took care of them as his own children, raised them and educate them. x
Because they dont have parents . they need someone that could help them. and nobody sees the love of terenty but the moon in the sky that floats. because for him love toward the children is greater than any thing.