My daughter is married to a man who has two grown-up children. If he were to die, would his children be able to claim from his estate?
If he made a will leaving everything to your daughter it’s unlikely his children would have any claim, unless he was supporting them financially at the time of his death. If he didn’t make a will the children may be entitled to a portion of his estate, depending on how much he was worth. If the couple’s house is in joint names, for example, it will usually belong to the survivor on the first death. Ideally your son-in-law should set up a trust, perhaps giving his children a share of his property after both he and your daughter have died.