Your question is kind of confusing to me, so I am trying to answer as best as I can. Please do correct me if I read your question wrong and made any wrong assumption because that can make a big difference on what's going on and what should be done. .
First question, what does your agent say about the contract situation?
If I understand you correctly, you made an offer on a house. The owner did not accept your offer and countered back to your offer. You then accepted the sellers' counter offer. In between, somebody else sent in another offer and now you are in multiple-offer situation?
As long as you are negotiating back and forth and there is no mutual agreement reached and until both of you agreed and signed at the bottom line, there is no binding contract between seller and buyer.
In real estate, time is of essence and a minute difference can make or fail a transaction.
In your case, the question is the timing. Were you within the time limit when you agreed to the counter offer? Did the 2nd offer come in in between? Did you agree to the exact term of counter offer and does the counter offer require certain signature which may or may not be there?
Unfortunately, we don't have your contract, because you have to read your contract, both original and counter offers really carefully before knowing what is binding and not binding in your situation and whether the second offer came in is viable - depending on if you are in contract at what time.
Then you asked the question about husband and wife team of Realtors. My first assumption is that the husband and wife team represent two different buyers and the seller is represented by a third agent?
Sounds like you have an agent who helped you with submitting your offer, then your agent's spouse bring in another offer for somebody else on the same house. This can be done, but should definitely be disclosed to both you and the seller. Hopefully one agent is not communicating with the other agent the exact terms of the contract as that would be a violation of fiduciary duty towards their own client (whichever buyer they are representing).
Again, if I made any wrong assumption, please clarify as your question does not have all the details and is sort of confusing to me.
One REALLY important thing to know is that contracts have very specific wordings and you really have to understand them clearly before knowing what to or not to do.