You can bring your parents and sisters under EU freedom of movement rules only if they are dependent on you or are members of your household (that is, if they have been living with you). If they qualify, then you can apply for their visas before you go to Ireland.
(If you have a spouse or other partner, or any children aged under 21 years, it is not necessary to prove that they are dependent on you or that they are members of your household.)
This is controlled by article 2, paragraph 2, and article 3, paragraph 2, of directive 2004/38/EC:
- ‘family member’ means:
(a) the spouse;
(b) the partner with whom the Union citizen has contracted a registered partnership, on the basis of the legislation of a Member State, if the legislation of the host Member State treats registered partnerships as equivalent to marriage and in accordance with the conditions laid down in the relevant legislation of the host Member State;
(c) the direct descendants who are under the age of 21 or are dependants and those of the spouse or partner as defined in point (b);
(d) the dependent direct relatives in the ascending line and those of the spouse or partner as defined in point (b);
- Without prejudice to any right to free movement and residence the persons concerned may have in their own right, the host Member State shall, in accordance with its national legislation, facilitate entry and residence for the following persons:
(a) any other family members, irrespective of their nationality, not falling under the definition in point 2 of Article 2 who, in the country from which they have come, are dependants or members of the household of the Union citizen having the primary right of residence, or where serious health grounds strictly require the personal care of the family member by the Union citizen;
(b) the partner with whom the Union citizen has a durable relationship, duly attested.
If your parents or sisters are not dependent on you or members of your household then you may be able to bring them through another immigration route under Irish law, but I do not know whether such a route exists.