@Brandon9000,
Your analysis Bran pretty much agrees with mine, the apparent discrepancy doubtless arising from my oversimplifications. I probably shouldn't have had us taking off from "nearby planets"
Also I had inadvertently reversed our roles. Returning to the OP I see it was I who kept going. Blame my age, 84 day before yesterday, incipient Alz's
Anyhow it's the guy who accelerates who stays young
So instead here are you and I 20 years old, approaching Earth where A lives, also 20. You apply your retros, joining A for lunch, where we're all three of course still 20. Much (much) later when I reappear (coming from the opposite direction?) A and you are very (very) old while I'm still 20
Sorry Bran if I was misunderstood. I am continually amazed at how easily misunderstandings arise
Incidentally I'd been making the assumption that my clock had stopped for my entire trip but I'm no expert. Perhaps owing to the curvature of space, my movement slowly resumes, reversing at the "halfway" mark, in which case upon my return we're all three the same old age. Just wild speculation