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
    cr1.data                as "Parent Name",
    e1.email                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
left join
    credentials cr1
        on r.Parent = cr1.AcctID and cr1.value = 1
left join
    email e1
        on e1.AcctId = r.Parent
where
    c.relationship = 'child'
group by 
    cr1.data, e1.email, cr.data, e.email
order by
    cr1.data

Parent Name	Parent Email	Child Name	Child Email	Amount	% of Amount
null	so@so	null	add@add	10.36	0.259000
John Smith	Test@Test	Jane Smith	email@email	24.72	0.618000