All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
The Mahrams (non-marriageable men) of a woman due to a marriage relationship are four: the husband’s antecedents, i.e. his fathers and grandfathers, his descendants, i.e. his sons, his grandsons, his daughters' sons and grandsons, her mother’s husband on condition that he consummated the marriage contract with the mother; and her daughter’s husband. As such, you know that your husband’s paternal uncles are not Mahrams and that the father of your husband’s mother is among the Mahrams to you, since he is included in the Saying of Allah, the Exalted (which means): {… their husbands' fathers …} [Quran, 24:31] that refers to all grandfathers, regardless of their lineage side.
Allah knows best.