Can I feed my grandchild?

If this is a serious question (which to me is virtually inconceivable), you are in a big bind. The staggering inappropriateness of this question indicates that even if you're able to keep your mouth shut about this, eventually you are going to do something to drive a wedge between your son and daughter-in-law. There will probably be an epic-scale ugly divorce, and your daughter-in-law will file court doents to keep you away from her child. You getting artificially inseminated and having your own kid at your age would be less psychotic than what you're suggesting. WHOA!