Here's an easy one:
You are so accustomed to my presence
that you often won't become aware of my absence.
Behold my clan, some proud, some meek,
all together one next to the other
and yet no trace of me.
Our encounters are usually just a squeeze,
got lucky though and dodged every attempt to capture me.
Have you found me yet?
Suspect the answer is
The letter $\,i$.
Because
'i' is the only letter not to appear anywhere in the riddle. The "clan" is the letters of the alphabet, all together except, most unusually, for I. And of course "I" would refer to itself as "me" when grammatically appropriate.
I don't believe this is the answer you're looking for but i think it fits
Are you?
a skin cell
You are so accustomed to my presence that you often won't become aware of my absence.
we shed skin all the the time without noticing the majority of the time
Behold my clan, some proud, some meek,
some skin is healthy, some is damaged by sun or tanning beds
all together one next to the other and yet no trace of me.
your skin cells are next to each other but you can't see any individual one
Our encounters are usually just a squeeze,
if you're touching any other part of yourself, your skin is making contact with another piece of skin, squeezing it together
got lucky though and dodged every attempt to capture me.
ALL dead skin doesn't always come off when showering or for women exfoliating
You are so accustomed to my presence that you often won't become aware of my absence.
We are used to the presence of fly because of their constant annoyance and sound that they make, but when they are absent we are busy with our activities and do not notice their absence
Behold my clan, some proud, some meek, all together one next to the other and yet no trace of me.
Some fly are big, some are small and we cannot differentiate one fly from another
Our encounters are usually just a squeeze,
When a fly comes near us we try to catch it with our palm as if we are squeezing a fruit or a stress ball
got lucky though and dodged every attempt to capture me.
It is very difficult to capture a fly
Have you found me yet?
Yes, you are a Fly.
