The new restaurants - named Pi Shop and Paco Tapas, will open alongside the relocated Casamia within the development of the former hospital on Lower Guinea Street.
Pi Shop, a 40-cover pizzeria will feature an open-plan kitchen and wood-fired oven and serve sourdough pizzas and ice cream. The restaurant, inspired by Casamia's roots as an Italian restaurant, will open all day for seven days a week from March 2016.
Peter's father Paco, who ran Casamia with his wife before sons Peter and Jonray took it over, is the inspiration behind Paco Tapas, a Spanish tapas restaurant.
The restaurant, which is scheduled to open next April, will serve constantly changing menus created by Casamia's chefs alongside an extensive sherry list.
Sanchez-Iglesias said: “It is amazingly exciting for us to be able to let people know about our two new restaurants Paco Tapas and Pi Shop. They will offer distinctly different options to guests, but in different ways both have been inspired by Casamia’s past. Whilst Casamia will continue to offer a fine dining experience, Paco Tapas and Pi Shop guests can expect to find a more casual place to eat, where you can grab a simple lunch or dinner made from the best ingredients around.”
Casamia, based in Westbury-on-Trym, will hold its last service on 23 December with plans to re-open at its new city-centre site in January.
The news coincides with the launch of website www.sanchez-brothers.co.uk through which customers will be able to book tables at all three waterside restaurants.