The charities, which are expected to merge in August 2016 under the name the Royal Society for Blind Children, described the merger as "a strategic effort to improve the life chances of blind and partially sighted children and their families".
The move builds on a formal association between the two charities agreed last year and follows the RBS’s merger with the Eyeless Trust in 2013. A spokeswoman for the RLSB said that expanding the charity’s geographical reach was also a key reason for the merger.
She added that while the merger was not financially driven, the charities expected it to bring significant savings and opportunities to increase income. and described it as a "merger of two equals".
The charities have 115 staff between them – 105 at RLSB and 10 at RBS – but it is expected that combined staff numbers will reach 250 over the next three years, the RLSB spokeswoman said.
She confirmed that any assets owned by either charity will be held by the new organisation.
The RBS and RLSB are two of the UK’s oldest sight-loss charities, at 151 and 177 years old respectively.
Tom Pey, chief executive of the RLSB, will lead the RSBC as its group chief executive. The RLSB spokeswoman said that the management of both organisations had already been combined because of the charities’ formal association, meaning no further changes are required.
She said that the individual trustee boards will be combined, with a reduction in trustee numbers expected during the next year.
According to the Charity Commission’s website, the RBS had an income of £1.1m in the year to 31 December 2015, with spending of £1.3m. For the same year, the RLSB had an income of £5.4m and spent £6.1m.
Pey said in a statement: "Our common goal is that no child should grow up to be poor or lonely just because they are blind. By bringing our two organisations closer together through this name change, we are better placed and better resourced to deliver the change these families and children urgently need."
He added that the trustees of both charities were finalising an investment plan for the new organisation.