Yes, definitely Younger and Elder and
Yes, those two labels are describing the relationship and
Yes it is likely to be father and son, BUT
it may also be worth checking:
first cousins ... or
uncle and nephew or
others on same branch.
The age difference between Younger and Elder does not need to be a generation or more.
Even in my lifetime, I have been shopping with my husband's Gran and also with my mother in law, and several sisters in law. Mother in law's sons are all known by their second given names. That is because each of them, when their dad registered their births followed his family practices and so first given name is always John.
So, in rural New South Wales, in the 1970s Mrs John SURNAME Senior, accompanied by Mrs John SURNAME Junior and Mrs John SURNAME the Elder, and Mrs John SURNAME the Younger and Mrs John SURNAME the Other Younger, would all shop together. I can assure you that we never experienced any mismatching of orders, Senior was mother in law of Junior, and Junior was mother in law of Elder and of two of us then Younger ones. but then again, we were shopping for supplies etc to cover 4 to 6 weeks and longer. None of us went anywhere near a butcher. Afterall, the fat lambs were the livestock on the family farms.
Now those of us still alive are no longer distinguished by labels reflecting our husband's given names. And our generation has likely overlooked explaining the practice of labelling relationships with elder/younger, or senior/junior or 1st, 2nd, 3rd, or I, II, III, IV etc.
JM