Not contradictory but misunderstanding rather. From my understanding, Op thought he can only buy the whole bitcoin at time and probably didn't have the financial strength to buy a whole coin and wants his brother to contribute half of the money while he also contribute half of the money too, so they can buy full coin. However, it's ridiculous he said he research about bitcoin but failed to find out that he can buy a portion of Bitcoin with any amount of money he has. I wonder what or which area he focused on while doing his research. Moreover, you don't have to involve anyone in your investment unless you are operating partnership from the beginning. Besides, you can still be into partnership with your brother and have your own personal investment. Partnership in crypto investment is not even ideal due to the nature of investment and its security measures.