MySQL 8.0

By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.

create table tbl(date_sundays date);
insert into tbl values 
('2022-03-06'),
('2022-03-06'),
('2022-03-06'),
('2022-03-13'),
('2022-03-13'),
('2022-03-13');

Records: 6  Duplicates: 0  Warnings: 0


select date_Sundays,
       date_add(date_Sundays,
                interval 7*row_number() over (partition by date_sundays order by date_sundays) day)
       as nextSundays 
from tbl


date_Sundays
nextSundays


2022-03-06
2022-03-13

2022-03-06
2022-03-20

2022-03-06
2022-03-27

2022-03-13
2022-03-20

2022-03-13
2022-03-27

2022-03-13
2022-04-03

date_Sundays	nextSundays
2022-03-06	2022-03-13
2022-03-06	2022-03-20
2022-03-06	2022-03-27
2022-03-13	2022-03-20
2022-03-13	2022-03-27
2022-03-13	2022-04-03