UK family visitor visa for mother and mother-in-law

[vignezh]

Dear seniors,

Thanks in advance for your input.

Background - My wife and I have ILR approved in April this year and would like to invite both my mother and wife's mother for a 3-month visit in October this year. My mother in law had her visitor visa approved last year and was in the UK from July to September and for 18 days in November before he visa expired. My mother had her visitor visa approved in October and visited for a month until middle of November (she had visa until feb this year).

First question - would it be okay for both of them to apply for a visit visa for October this year as you are only allowed to stay in the uk for 6 months in a year? in our case, would the 1 year starts from when they were first issued their visitor visas or is it calendar year (Jan to Dec).

Second question - would it be okay for them to apply at the same time as I will be sponsoring both of them and they will use the same documents.