Suppose Object A is exerting gravitational force on Object B. Object A increases in mass, and so increases in volume, increasing the gravitational force on Object B. But, since mass occupies space the objects will need to be moved apart in order to keep them from joining. But as Object B is moved away from Object A.

Eventually Object A turns into a black hole, which further complicates the issue. Due to the event horizon, so it's radius is a definite minimum distance between the objects.

Is there some sweet spot of maximum gravity?