jmj9905

Back in october I booked 1st class award seats for my wife, son and I to lhr. I had to book my son and wife on a different flight because of award availability.
They are booked dca/ord/lhr rt. I had to book myself ord/lhr/jfk. My ord flight was different from theirs. A seat on their flight opened by EF notification and I got myself booked in 1st on their outbound flight. The other day I got an e-mail from ef that the return flight my family was on had one seat available. I called aa plt to change and was told I could not do this. The reason given was that this was a ow award versus an all partner award(we are going on from lhr to bud & prg). I was never told this when I booked the awards. How do you know this if you are not told? I do know there are different rules but where do you find them?
Thanks!