Yes, it is difficult for children to realise that their mom or dad is actually an independent person with their own needs and desires. Being eternal child seems to be the desire of the younger ones and have their parents always put them in the first place and renounce on their own lives — as so many moms do, and also dads.
It is time for grown up children to REALLY grow up and to release the parents from their projection on them. It is time that the younger people realise that older people have the same desire for connection and sexuality and that they stop resenting their parents for finally live their own life. It is time for shadow work on the expectations we/you have on others and on the feeling of entitlement that the older ones should be there for the younger ones eternally. It will come the time where it should be the other way round and the younger ones can show their gratitude to have been in the very first place for so many years, even decades!