do we know if the Modliszewski had a crest or coat of arms?
In Polish heraldry, sometimes a singe crest, originating with a single noble family, is shared by hundreds of unrelated families who adopted it as a result of fighting together or collaborating in some way. Sometimes these families would change the design of the original crest slightly to customize it and make it their own.
I did a search and the only crest I could find with a squirrel was that of the Bazenski family. It's possible that your family adopted this crest and modified it to have two supporting squirrels. There are some variants of this crest for sale on the internet but I suspect they've been modified in modern times to be politically correct and remove the black man. Apparently the original holder of the crest defeated a Moor in battle and that's what the black man signfies.