consult a pro. without knowing the provisions of his trust we can't tell you who inherits his interest. it could be the trust or it could be his spouse or it could be someone else.
there are various filings that the partnership must do so the heir gets the benefit of the step-up in basis - election under 754 to apply the provisions of IRC sections 734(b) and 743(b). in some rare instances, this may not want to be elected.
income gets allocated for his interest based on the number of days he was alive. but the heir then may reduce their share of income or loss if electing basis adjustment. a pro can look at everything to give the best advice.
