My DB in his 40s has never made much of an effort with my 2 DCs. They are now adults and have moved out of the family home and work. For many years through all the childhood he rarely sent them birthday cards . He stopped giving the xmas presents when they got to about 18- fair enough. He lives some distance away and doesn't see them from one year to the next, but I'm a bit sad that he made no effort at all to create any kind of relationship with them. he's unmarried, no kids, never had along term relationship- so in some ways his behaviour doesn't surprise me, but we are otherwise a close family- our parents are still alive in their 80s and they make quite an effort with my DCs.