IF you have authority to bind "your partner"....which it appears you have been given; then since you have SIGNED the offer accepting Couple B's offer and accepted their check, then Couple B would arguably be in a position to SUE for completion ......so DO NOT complicate matters further by accepting TWO OFFERS!!!!
We suggest you choose a law firm to assist at your earliest...
Weir & Associates
Solicitors & Notaries
16th Floor Tak Shing House
Theatre Lane
20 Des Voeux Road Central
Central
Hong Kong
Tel : 2526-1767
Fax : 2868-3568
email :
WeirLaw@HongKongLaw.com
www.HongKongLaw.com/weirlaw