From what I've seen of some families, it can be the grown-up children that can cause problems for a bereaved parent who wants to re-marry. Plaintive yelps of "What about our memories of Mum" are often the response to a widowed father who's maybe spent years alone before he's able to form a new relationship.
My lady and I have made it plain to all our children that neither of us wishes for the surviving partner to remain in enforced loneliness for the rest of their life. And we're both OK with that.