Basics are DB's DD has been married twice. Two DCs from first marriage one from her second. There is also a DSS from her DH's first marriage. DSS is the same age as eldest DS. Access had always been flexible, they live in the same village as DSS's DM. Now DSS is older (16) he comes and goes as he pleases, more or less. All very friendly.
Only one hiccup up until today. First Christmas after the marriage DB and DSisIL spent the same on DSS as on their grandchildren. DSS's grandparents gave token presents only. All families very, very comfortably off. Son in law was embarrassed and asked that they buy token presents only as well because his family thought that was best, to spend more on their blood grandson. Fair enough. That's how it's been for 5 years.
DB and DSisiL have to rewrite their wills because they've sold a property they used to rent out. The DGCs are a lot older now than when they wrote the previous will and they were thinking it would be better to let them have the money they were going to be left sooner rather than later. Their plan was to buy each of them a car and also a lump sum for university.
Son in law says this isn't fair unless they do the same for his son. DB told him that's not how it works in their family at his parents' choice and he wasn't going to change the rules now. There is nothing to stop Son in law's parents doing the same. They are very well off with multiple holidays abroad. They are very generous at Christmas and birthdays but otherwise prefer to spend their money on themselves. Fair enough.
DB still intends doing what he planned with his DD's approval. But I wonder if he is being a bit U.