Hi Gunjan Gadodia

Here's a silane that boasts the best suitability for fibreglass: The Best Silane Coupling Agent -Specially for Fiberglass (hengdasilane.com)

https://www.hengdasilane.com/the-best-silane-coupling-agent-specially-for-fiberglass/#:~:text=HENGDA-E8133%20is%20an%20amino%20functional%20silane%20couple%20agent,99.5%20%2B%20and%20has%20the%20world%E2%80%99s%20top%20level.

I'd think that bonding fibre glass may be similar to bonding to glass and so Methyl Tris(methylethylketoxime)silane (MOS) may also be suitable.

I see that some silicone sealants use a combination of silanes as shown here:

https://krayden.com/pdf/xia_sealant_formulation_materials.pdf

I hope this helps,

Best

Phil