GIVEN what a mouthy thing I grew up to be, it’s shocking to me that I began talking later than most children do. But I didn’t need words. I had my older brother, Mark.

The way my mother always recounted it, I’d squirm, pout, mewl, bawl or indicate my displeasure in some comparably articulate way, and before she could press me on what I wanted and perhaps coax actual language from me, Mark would rush in to solve the riddle.

“His blanket,” he’d say, and he’d be right.

“Another cookie,” he’d say, and he’d be even righter.

From the tenor of my sob or the twitch of one of my fat little fingers, Mark knew which chair I had designs on, which toy I was ogling. He decoded the signs and procured the goods. Only 17 months older, he was my psychic and my spokesman, my shaman and my Sherpa. With Mark around, I was safe.

This weekend he’s turning 50 — it’s horrifying, trust me — and we’ll all be together, as we were at his 40th and my 40th and seemingly every big milestone: he and I and our younger brother, Harry, and our sister, Adelle, the last one to come along. We marched (or, rather, crawled and toddled) into this crazy world together, and though we had no say in that, it’s by our own volition and determination that we march together still. Among my many blessings, this is the one I’d put at the top.