The Balarins, currently executive creative directors, and joint heads of strategy Gallery and Mackay will now formally take on the day-to-day running of the London agency, which works with brands including Ikea, Moneysupermarket.com and Stella Artois.
The quartet will report to global chief executive Michael Wall and Mother founder and chairman Robert Saville. The foursome has effectively been running Mother London for the last 18 months and their promotions solidify that role.
Saville said: "For me, this is a phenomenally pivotal moment. Having worked for ten years with these guys, they are people who love Mother in their hearts and souls. We're coming up to 21 years and this is about what's happening for the next 21 years."
Mother Holdings has diluted its ownership of Mother London in order to give the new partners equity in the agency. Saville declined to comment on how much the changes valued the agency at or how the new partners financed their equity.
This is the first time Mother has appointed a broad team of partners to run the agency as a team since the original line-up of Saville, Stef Calcraft, Mark Waites, Andy Medd and Matthew Clark. It appointed Williams and creative director Stephen Butler as additional partners in 2010 but both have since left.
Wall said: "It's been a real pleasure to work directly with such a talented and likeable group and to help them to achieve this much-deserved recognition. I'm excited about what they will bring to Mother’s next iteration."
Mackay said: "We are bursting with pride. We feel quite overwhelmed and are absolutely delighted to be taking the helm. [Our appointments are] a statement of future intent. Mother is absolutely determined to remain independent."
Mother promoted Ana and Hermeti Balarin to executive creative director in June 2015, making them the first creatives to hold the title at the agency. The husband-and-wife duo joined Mother on placement in January 2007.
Gallery and Mackay became joint heads of strategy in January 2014 after the departure of Dylan Williams. Mackay joined Mother from Publicis in 2008, while Gallery moved to the agency in 2009 from McCann London.