Cousins who were close as kids can pick right back up at a wedding twenty years later.

Some relationships keep without maintenance. Childhood closeness gets stored differently from adult friendship, so two cousins who spent every summer together can go twenty years without a conversation and still find the whole thing intact at a wedding, because what they share is a period rather than a routine. That does not make contact pointless. It means the floor is higher than you think.

If you have lost touch with somebody from that part of your life, you can reach out with no apology for the gap. Skip the summary of the last ten years. Start with something from back then and see what comes up.