It occurs to me that all the characters who had kids gave birth to daughters. Lou and Edie had three daughters, as did Murray and Marie. Phyllis and Lars had Bess. Ted and Georgette had Mary Lou.
Yet both Murray and Ted adopted sons. Just an observation.
Well, in "Farther's Day," we do get to see Ted's father (Liam Dunn).
We also get to see Murray's stepfather (Lew Ayres) in "Mary and the Sexagenerian."
So there were a couple of of "sons" on the show.
Just speculating.
With Phyllis my guess would be the writers felt a boy would have been out of place in scenes mostly around three adult women.
Lou and Murray having daughters might better explain why Lou decided to hire her and why her and Murray became such good friends.
That makes sense. TV series often do things to facilitate episode plots, rather than to be statistically typical.