SQL server duplicate records issue - sql-server

Question

I have two source tables CustP and CustS (this table is only to store email id, this is how current design is)
CustP:
CustID Fname Lname Phone
------------------------------------------
100 John Doe 1234567890
200 John Doe 1234567890
300 John Doe NULL
CustS:
CustID Fname Lname Email
--------------------------------------------
100 John Doe NULL
200 John Doe a#a.com
300 John Doe a#a.com
I would like to identify duplicate records from above 2 tables based on below criteria :
if (FName, Lname and phone matches) OR (FName, Lname and email matches)
Below are the steps I am using to generate the duplicate result set
drop table #AllCustomer
select
cp.CustID, cp.Fname, cp.Lname, cp.Phone, cs.Email,
ROW_NUMBER() over (order by cp.Fname) RN
into
#AllCustomer
from
CustP cp
inner join
CustS cs on cp.CustID = cs.CustID
--Combining the customer and matched customer into a temp table
Select
A.CustID CustID, B.CustID MatchedCustID,
A.Fname FirstName,
A.Lname SurName,
A.Phone Phone,
A.Email Email,
B.Fname MatchedFirstName,
B.Lname MatchedSurName,
B.Phone MatchedPhone,
B.Email MatchedEmail
into
#AllMatchedCustomers
from
#AllCustomer A
inner join
#AllCustomer B on (A.Fname = B.Fname
and A.Lname = B.Lname
and A.CustID <> B.CustID
and A.RN < B.RN)
where
A.CustID <> B.CustID
and (((1 = case
when isnull(A.Phone, 1) in (isnull(B.Phone, 2))
then 1
else 0
end))
or
(A.Fname = B.Fname and A.Lname = B.Lname and
isnull(A.Email, 'A') = isnull(B.Email, 'B'))
)
And the result is as shown below
CustID MatchedCustID FirstName SurName Phone Email MatchedFirstName MatchedSurName MatchedPhone MatchedEmail
100 200 John Doe 1234567890 NULL John Doe 1234567890 a#a.com
200 300 John Doe 1234567890 a#a.com John Doe NULL a#a.com
I need help in identifying if Cust100 is matched with Cust200 with phone number and cust200 Is related to cust300 via email , then result should include one more additional row showing Cust100 and cust300(because a=b, b=c therefore a=c). (here it would be 100 and 300 in the 3rd row of result set). Or what are the alternative approaches? Appreciate your help, thanks in advance.