Plum, apricot, almond, peach, same family

[maraxxl]

It is correct to say plums, apricots, almonds, peaches belong to the same family but so do apples, pears, quinces, roses (rose family)... I guess what you actually had in mind was to stress the fact that they belong to the same genus: prunus as in prunus persica (peach) or prunus armeniaca (apricot) That matters a lot not just in terms of grafting but especially here.

[maraxxl]

@maraxxl

It is possible to graft a plum, an apricot, an almond, a peach and even a cherry on the same prunus rootstock but do not try to add e.g. an apple or a rose.