Imagine family gatherings of siblings, aunts, uncles and so on, gathered around sharing memories, how those conversations drift. That's part of the nature of conversation.
That said, the OP might give some thought to their goal for the thread and be mindful how well their first post might frame the intent of the discussion.
If folks decide to go off on a tangent, others might politely reign in the dialogue back on track.
Or wave a white flag and move on.