[robhlt]

You could use a call/SMS forwarding app on an old android phone. I haven't used any myself, but I know they're popular with small businesses.

Basically just get an old android phone, put a prepaid SIM in it, and leave it charging at home somewhere. The app will forward calls/texts to any other number(s) you choose.

[tcrhelpforsms]

Forwarding is only half the requirements here though. Sending responses from a different number will generally lead to confusion, and further messages from the sender will not necessarily be shared. Though maybe if the sender is savvy enough with group texting it might work out okay.