yes no probs i have done it many times.
You will not however be allowed to insure more than one person on them.
I.E. 1 rider insured on 2 bikes no problem OR 2 riders on 1 bike, not 2 riders on 2 bikes.
With insurance there are exceptions if you want to pay but this is what my insurers said when i enquired about insuring a mate on my mille when i had a 2nd bike on the policy.