All perfect praise be to Allah, The Lord of The Worlds, and may his peace and blessings be upon our Prophet Muhammad and upon all of his family and companions.
Trade-mark is ensured according to Sharia because it has a value in the contemporary Fiqh jurisprudence, since the International Fiqh Assembly issued resolution No.43 (5/5) regarding intangible assets what follows:” First: Trade-mark, business address, brand, authorship and invention are considered private rights of their owners; nowadays and according to the modern custom, they are considerable material value for financing people. Therefore, violating these rights is impermissible as they are considerable in Sharia.”
In conclusion, the value of the trade-mark belongs to all heirs including your father and it should be distributed among them in accordance to their shares, but if some of the heirs were seeking to have all its value for themselves, then other heirs are required to file a suit to demand their share in a Sharia court. And Allah knows best.