Selling %'s of co-owened property question?

[vicckav]

OREGON Iam co-owner of a 3 acre lot with house with my 2 sisters and 1 brother, and have been living on the property in the house since my uncle died in 1994. My share was 20% and they each had 24.6%. In 2006 I sold 8% of my 20% to a friend at between $650.00 and $1000.00 per %,and did not tell my sisters and brother about it. Well about 3 months ago they found out about it and are very upset with me, also that person is no longer a friend of mine for other reasons. My question is: Was it legal for me to sell those 8% without the co-owners consent? I need a answer A.S.A.P. Also I don't always have access to a computer to receive the answer to this question, so I am leaving my number. 503 935 3775 Thank-you