Can You Have More Than One Gemheart?

[Trusk'our he/him]

For instance, if someone used Hemalurgy to give themselves the ability to grow a Gemheart, could you grow multiple if you were a Singer and already had one, or if your just gave yourself multiple spikes providing that ability? Could someone who did this bond multiple Spren? Would a Fused with multiple Gemhearts be able to hold more Voidlight?

[Quantus he/him]

No real evidence, but if you already had one and spiked the ability in addition, I think it would pool (like allomantic abilities, for example) and give you a bigger and/or denser Gemheart, rather than two.  Same as how spiking Senses increases them but does not grow new body parts.