How to Left Join two Parent-Child tables (i.e. 4 tables) - sql-server

Question

We have the following database structure:
How can we query for all the data that belongs to a specific client and group? (An example written using Entity Framework 6 would be great.)
We could do something like this:
var parentChild1 = dbcontext.Parent1.Include(p => p.Child1).Select(p => p.ClientId = clientId).ToList();
var parentChild2 = dbcontext.Parent2.Include(p => p.Child2).Select(p => p.GroupId = groupId).ToList();
// And the manually join the values in parentChild2 with the objects in parentChild1.
// But there has to be a better way than this.
I'm thinking something like this; but can't figure out how to wire up child1(s) with child2(s):
void GetData(int clientId, int groupId)
{
var query = (from p1 in dbcontext.Parent1
from c1 in dbcontext.Child1
where p1.ClientId == clientId && c1.Parent1Id == p1.Id
join p2 in dbcontext.Parent2.Where(p2 => p2.GroupId == groupId)
on p1.Id equals p2.Parent1Id into p2groups
join c2 in dbcontext.Child2 on c1.Id equals c2.Child2Id into c2groups
from p2g in p2groups.DefaultIfEmpty()
from c2g in c2groups.DefaultIfEmpty()
select new Parent1
{
Parent2s = p2g,
//Child1s = c2g ??? How to wire up child1s with child2s?
};
}

Answer 1

The following sql statement should return all the data that belongs to a single parent1Id and groupId, from all the tables.
SELECT *
FROM Parent1 p1
LEFT JOIN Parent2 p2 ON(p1.Id = p2.Parent1Id AND p2.GroupId = #groupId)
LEFT JOIN Child1 c1 ON(p1.id = c1.Parent1Id)
LEFT JOIN Child2 c2 ON(c1.id = c2.Childe1Id AND p2.id = c2.Parent2Id)
WHERE p1.Id = #Id
The child joins are left joins since I assume not all parents have children, but the parents join is an inner join since you need the groupid as well as the parent1 id.