Tithing is Old Testament law. We are not under the OT law. We are under GRACE in the New Testament.
The New Testament says to give what you want cheerfully, and if you don't want to give, then you don't have to.
Read 2 Corinthians 9:7, and they should use the money to help the mother.
And read THIS ESPECIALLY:
1 Timothy 5:8 "But if any provide not for his own, and specially for those of his own house, he hath denied the faith, and is worse than an infidel."