My Patriarchal Blessing tells me I’m of the House of Joseph & the House of Ephraim. That I can receive a double portion of blessings. Can a person be of two houses? What does it mean? What are my responsibilities?
Joseph, who was sold into slavery by his brothers into Egypt, had two sons: Ephraim and Manasseh. As a descendant of Ephraim you are also a descendant of Joseph. You can read in Genesis 48 about the blessings of Joseph and of Ephraim (and also Manasseh). Don’t forget to delve into the scripture references found in the footnotes!
Your responsibilities (really every member’s responsibilities) could be summed up in 2 Nephi 31:20
Wherefore, ye must press forward with a steadfastness in Christ, having a perfect brightness of hope, and a love of God and of all men. Wherefore, if ye shall press forward, feasting upon the word of Christ, and endure to the end, behold, thus saith the Father: Ye shall have eternal life.
If you want specific insight, it may not be out of the question for you to ask to follow up with your stake patriarch.
Here are a couple other resources for your research:
What does it mean to be from the lineage of Joseph?