I dont think it is selfish at all to say no.Why on earth is it expected that hand hold our children through their adulthood ? Is it really our job to provide grown men and women with a house, money, childcare and all else they demand ?
The argument that they have such busy, hard, stressful, and expensive lives does not stand up when they manage to have date nights, weekends away, new clothes every month and dont buy the cheapest house on the market.
They are adults and make an informed choice when they decide to have a family
New house and a sloping garden