COS period advice for PBS extension

I got COS with 3 years of validity in 2020. It's due to expire. My partner and child joined me 1 year later and they hold a dependent visa since 2021. If I get a 2 year COS for extension I will be eligible for ILR in 2025 but my partner won't be eligible until 2026. Shall I ask my employer to provide 3 years for extension so that my partner and child will get a dependent visa till their ILR eligibility? Will there be any challenges if I get 3 year COS instead of the usual 2 years COS for extension?

Yes, you can ask for a CoS for 3 years. No issue.

Thanks a lot for your response. If my employer provides COS for only 2 years then they will get visa end date same as mine . so when I apply for ILR can I include as ILR dependents or PBS dependent extension same time or they need to apply only after I got ILR as ILR dependents? Also they just need only 1 year for ILR eligible. Can they get a PBS dependent extension for 1 year?

If you get a 2 year cos, then they can apply separately for a pbs dependent extension andust apply before their visas expire. It will be a 3 year extension. You cannot apply for only 1 year, the immigration rules state it will be 3 years if the main pbs migrant has ILR or British citizenship.

Thanks again. Since all of us have the same expiry date, Can they apply at the same time while I apply ILR as ILR dependents or do they need to wait till my ILR is success?

They do NOT apply as "ILR dependents", this is a completely different visa category and will reset their ILR clock to zero.

They apply as pbs dependents on their own form either when you apply for ILR or once you have ILR but before their visa expires.

Simplest would be to ask for a 3 year cos.

Sure my first option is to ask 3 year COS. In that case do I also need to wait till 3 years to apply for ILR since I have visa valid for 3 years or will there be any challenge if I apply in 2 year itself when I become eligible even though I have 1 year valid visa remaining?

You can apply for ILR when you qualify.