youngest of his siblings [closed]

I have a problem with this sentence:

He was one of the youngest of his siblings.

The meaning should be clear: he had many brothers and sisters, and he was one of the youngest of the lot, but the expression feels awfully awkward to me, with expression his siblings implicitly excluding the subject from the set; you're not your own sibling, so you're not one of your siblings.

Is there a better way to convey the idea without getting too muddled with details and without losing the meaning? A collective expression for all of own siblings plus self maybe?

• Eldest of the children have children of their own, so he's not one of the youngest in the family.
• His parents have siblings who have their children, so he's not one of the youngest in his generation.
• "One of the youngest of his parents' children" while technically correct is awfully roundabout way to convey it.
• He's not the youngest, so he's not just "younger than his siblings". "Younger than most of his siblings" might work but still feels somewhat awkward.

As mentioned in my comments, I believe "of his" is unnecessary since it is implied. This results in the 'less awkward' phrase:

He was one of the youngest siblings.

Since "he" can't be part of someone else's siblings, "his" siblings are implied. If you want to compare the subject with someone else's siblings then you would have to explicitly state this. You could perhaps say, "He was one of his youngest siblings" - but again unnecessary in my opinion, since you are simply reiterating the subject.

What about simply "He was one of the youngest of his immediate family"?