It is difficult I know. We go from being one of the lynch pins of family life for decades and then gradually this drifts away from us, and it is easy to feel like a total irrelevance.
It is especially difficult at the moment as, rather than being someone for my family to turn to, I have become someone for them to worry about since my heart episode and stent. I would not choose to be that person. But that is inevitably the role I am now cast in.
Another mild blow is that the holiday I have gone on with one DD and family for many years at Easter is not going to happen - they are going elsewhere. They have suggested that I might like to hire a small place where they are going, but it feels very different from being invited along. I get it - they have busy lives; they want their holiday to be a real relaxation rather than a week of having to take me into account with my dicky ticker and mobility problems - I totally understand and endorse that, but it is one more thing to get a grip on - one more loss in a whole succession of losses.
Interestingly my friends see me in a very different way. They are kind and concerned when my health problems hold me up in some way, but they see me as many other things: choir leader, concert trip organiser, publicity designer, village hall trustee, active U3A member etc. etc. But I guess they do not have the same sense of responsibility as family.
Like the OP, I have to bite the bullet on the fact that one of my DD's MILs is being much more involved in child care this half term because she is 10 or more years young and much fitter.
It is a time of transition - I do not wish to speculate towards what!!