Need to check on the check-in luggage.

I've book flights individually for 2 person with 2 booking confirmation number but both flying on the same flight and we will have to online check-in separately (since online check-in only able to check-in 1 booking number at once). When we drop off our baggage at airport, each with 20kg luggage capacity which means 40kg for both, can AA take in ONLY 1 luggage with 40kg for 2 separate bookings on the same flight?