will definitely be the sponsor and it doesn't matter wether they work in the same company or not as long as they have complete requirements to show at the immigration
1. authenticated MC
2. RP (husband and wife)
3. baby's passport
4. birth certificate(baby)
5. green card from HMC with blood group
6. baby picture
7. RP application form
No need for NOC and Salary Certificate since the baby was born here.