In-laws Are Trying To Make Us Pay Off Their Loans

My spouse and I have been no-contact with their parents (my in-laws) for nearly two years now for a number of reasons related to past conflict/abuse and ongoing toxicity within the family dynamic. Recently, my FIL somehow managed to leave a voicemail for my spouse (despite us both having his number blocked) suggesting that he and MIL expect us to pay off the Parent PLUS Loans taken out by MIL for my spouse's undergrad college tuition prior to the disconnect.

As mentioned, these loans were taken out by my MIL, who has worked a public service job for 20+ years and qualifies for public service loan forgiveness. My parents (also public sector) got their student loans and Parent PLUS loans forgiven several years ago through the program, at which time I asked them to give the information on the process to MIL so she could get her loans forgiven along with any she took out as PLUS loans for my spouse and their older sibling. I have confirmation and am getting screenshots of said conversation surrounding this (which I followed up with MIL about at the time) sent to me as proof that this occurred.

My question is, do they have any legal footing to force us to pay these $100K+ loans, despite them being taken out by MIL? There was a verbal understanding made when my spouse was 17 that they would pay back the loans, but nothing was ever signed/notarized or even put in writing. Their sibling is older and has made payments as an authorized payer.

Additionally: a family member of my spouse left them some inheritance a few years back that won't be released until after their partner passes. Would MIL/FIL have any standing to contest the will given our falling out, even though they were also left a good sum? For reference, said family member lived in Canada, and we're in the US.

Any suggestions, advice, etc. are much appreciated. We're barely out of grad school and terrified that this will nuke our already shoestring finances for the foreseeable future.