I've had unknown relatives make contact with me twice, and twice I've made contact with relatives of my OH.
One of the rellies of my OH was inquisitive without proffering any help/info/contact himself. He asked for too much personal information, in my view. I even write out by hand a complete family tree of that side, and posted it to him in Australia, never getting a "thank you" or aknowledging the many hours of careful work involved. He sounded rather unpleasant in his e-mails, his written English was poor, and we have heard no more from him, for which we have no regrets.
The other rellie of my OH was delightful, sought me out through an online group, later visited us, to be shown round some old time haunts of her grandfather, with her own parents, one of which proved to be my OH's cousin, and proffered information on their own links, which he had known nothing of, previously. We are still in touch.
What a contrast!
On my own paternal side, one very pleasant contact, with a cousin of my father, which has resulted in a gentle "keeping in touch" ever since.
Either way, you never know until you essay it.
TY