Ifyou are on the settled status scheme already they should be able to apply to join you after June. If you are not on the settled status scheme yet then no they will not be able to apply for a Family Permit after 30 June 2021.
As the family member who is EEA national and based in the UK you will need to show that:
1. you have been living in the UK by 31 December 2020
2. have been working, looking for work, studying or self-sufficient while living here
3. have a right of permanent residence in the UK - here being on the settled status scheme will suffice
The documents necessary for all your 3 family members to provide when they apply are:
1. valid passport
2. 2 passport size colour photographs
3. evidence of their relationship to you – for example a birth certificate, marriage certificate, c
4. your valid passport or national identity card (or a certified copy if you cannot provide the original)
5. evidence that you as the EEA national have been resident in the UK by 31 December 2020. If you have been in the UK for more than 3 months, they must show that you have a permanent residence document or provide evidence that you are:
a)working - for example an employment contract, wage slips or a letter from an employer
b) self-employed - for example contracts, invoices or audited accounts with bank statements
c) studying - for example a letter from the school, college or university
d) financially independent (‘self-sufficient’) - for example bank statements
You must have full health insurance (comprehensive sickness insurance) if you are studying or self-sufficient. This is not necesary if you are working.
Any clarification please do not hesitate to send your follow up question. I am glad to help. All the best.