SQL Server 2017

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WITH email AS (
    SELECT '1a2b' AS AcctID, 'Test@Test' AS EMAIL UNION ALL
    SELECT '2a3b', 'email@email' UNION ALL
    SELECT '3a4b', 'add@add' UNION ALL
    SELECT '4a5b', 'so@so'
),
credentials AS (
    SELECT 1 AS value,'John Smith' AS Data, '1a2b' AS AcctID UNION ALL
    SELECT 2, '123 Main',   '1a2b' UNION ALL
    SELECT 3, 'US',           '1a2b' UNION ALL
    SELECT 4, '555-555-5555', '1a2b' UNION ALL
    SELECT 1, 'Jane Smith',   '2a3b' UNION ALL
    SELECT 2, '456 Main',     '2a3b' UNION ALL
    SELECT 3, 'RU',           '2a3b' UNION ALL
    SELECT 4, '111-555-5555', '2a3b' 
),
class as (
    SELECT '1a2b' AS AcctID, 'Parent' AS Relationship  UNION ALL
    SELECT '2a3b', 'Child'  UNION ALL
    SELECT '3a4b', 'Child' UNION ALL
    SELECT '4a5b', 'Parent' 
),
relationship as (
    SELECT '1a2b' as Parent,  'Jan 2019' as Date, '2a3b' as Child Union ALL
    Select '4a5b', 'Feb 2019', '3a4b'
),
amount as (
    select '1a2b' as AcctId, 10.05 as 'amount' UNION ALL
    select '1a2b', 15.01 Union ALL
    select '2a3b', 12.36 UNION ALL
    select '3a4b', 10.36 UNION ALL
    select '2a3b', 12.36 UNION ALL
    select '4a5b', 26.36 
)

select
    r.parent                as "Parent Name",
    r.parent                as "Parent Email",
    cr.data                as "Child Name",
    e.email                 as "Child Email",
    sum(a.amount)           as "Amount",
    (sum(a.amount)*2.5/100) as "% of Amount"

from 
    email e
join
    class c
        on e.AcctID = c.AcctID
left join
    relationship r 
        on c.AcctID = r.child
left join
    amount a
        on e.AcctID = a.AcctID
left join
    credentials cr
        on e.AcctID = cr.AcctID and cr.value = 1
where
    c.relationship = 'child'
group by 
    e.email, c.relationship, c.acctID, r.child, cr.value, e.acctid, c.acctid, r.parent, cr.data
order by
    r.parent

Parent Name	Parent Email	Child Name	Child Email	Amount	% of Amount
1a2b	1a2b	Jane Smith	email@email	24.72	0.618000
4a5b	4a5b	null	add@add	10.36	0.259000