Multiple connections from same IP

[Juve]

Hi all, I am using the shrew.net vpn client in mobile clients configuration. I've got two remote guys who need to connect to our pfsense using ipsec from the same location. It seems they can't connect at the same time. I have moved them from PPTP to IPSEC because of that king of problem with GRE not supporting parallels tunnels to same destination, is that the same with IPSEC ?
They use PSK and FQDN as identificator, each guy got his fqdn : guy1.test.com and guy2.test.com and his own PSK. Am I doing something wrong or is this a protocol (design) limitation.

Thanks.