These are neither SLRs nor RCTs but the subject matter is relevant. This available on ResearchGate and may be of interest; however, I have not accessed the full text:
Hanley, T. (2009). The working alliance in online therapy with young people: Preliminary findings. British Journal of Guidance & Counselling, 37(3), 257-269.
These relate to children but include the parents also:
Vossler, Andreas (2004). The participation of children and adolescents in family counselling: The German experience. Counselling and Psychotherapy Research, 4(1), pp. 54–61.
http://oro.open.ac.uk/17212/2/3670A724.pdf
Wade, S. L., Wolfe, C., Brown, T. M., & Pestian, J. P. (2005). Putting the pieces together: Preliminary efficacy of a web-based family intervention for children with traumatic brain injury. Journal of Pediatric Psychology, 30(5), 437-442.
I have been unable to access the full text of this paper:
King, R., Bambling, M., Lloyd, C., Gomurra, R., Smith, S., Reid, W., & Wegner, K. (2006). Online counselling: The motives and experiences of young people who choose the Internet instead of face to face or telephone counselling. Counselling and Psychotherapy Research, 6(3), 169-174.
In your question you did not indicate whether or not you had searched any published literature databases, such as Pub Med. If you did this and the results were unproductive, please can you say why you think that this might have been the case and why we should be able to do better. This may alert ResearchGate members to focus on published studies which provide only indirectly help to answer your question or on relevant studies which are still in progress.