Some advice please?

Hi all. Could someone offer some advice on my obligations here?

Background to the case:
moved in with my ex and her son from previous marriage in June 08. Had my son in June 09. Relationship Broke down in November 11, ex moved out with children in February 12. Immediately began court proceedings for shared residence of my biological son. Was told by a solicitor on a free consultation that I had no chance of seeing step-son (SS) again unless she agreed.
Currently waiting for Cafcass report before next hearing and found out that there was a provision in the Children Act as we (me and SS) had lived together for 3 years.

Applied to vary existing proceedings to include contact with SS.

OK

I sent a copy of the application to her solicitor. I didn''t have my SS''s biological father''s address, but he is respondent 2 on the C2 form. I sent a text message to an old mobile number of his I had, just to say I needed to post some paperwork to him. No answer so I phoned and got through to his mother (i.e. my SS''s grandmother).

She wouldn''t give me an address, and very soon after that I got a text from my ex telling me to leave them (SS''s dad and grandmother) alone, that neither her or his dad would support any application for contact and that SS''s dad had forwarded on my text message to ex''s solicitor. She said that anything I needed to send on could be sent via her solicitor.

Am I obliged to continue to trying to contact the father. He is a respondent in proceedings, but has refused to give me an address, won''t get in contact with me and is obviously siding with ex.

I have made an attempt to get in contact, is that the end of my obligation.

Also, because I want to keep this at the forefront of my mind, what should I do? My conscience says to carry on with it, but I''m scared of being wrong. I''m hoping that Cafcass will at least consider SS''s feelings

I hate doing this but BUMP!