I did research with a professor during my senior year (2017/2018) and we published a paper together. He wrote me a letter of reference for my grad school applications.
One of the professors I'm interested in working with at another school is his sister-in-law. I've tried emailing her to no avail. I had a friend suggest I have the professor I know email her instead, since even the fact that they're related aside, a professor is more likely to respond to an email by another prof.
This is identical to this question: How do I politely ask a professor to contact another professor he knows to accept me as PhD student?
However, the answer to the previous question suggests subtlely bringing it up during a conversation. I'm not in school anymore (just graduated) and don't meet this professor in person anymore so I need to do this via email.
I was hoping someone could give some advice about how to compose an email politely requesting him to contact his sister-in-law on my behalf? I feel fairly embarrassed having to do this since I am asking for quite a bit of him, but I figure it's worth a shot. Worst case he says no.