I am putting the only part from attached xml , which is required here to understand the issue.

See below : The XML which we received has three <Application/> nodes , separately for every individual enrollment . This employee has enrolled for himself and two children’s separately in a single product(ProductID="13811").
As we all agreed that, Workterra should receive only Single plan enrollment details(Single <Application> node) for which employee gone from Workterra to Selerix. In Workterra we have configured single plan for “LBT” , which allows Spouse and Children enrollment along with employee enrollment. From Workterra we send employee , spouse and child demographic details to Selerix.

For Critical Illness and Accident plans, we are receiving the proper response. Even for LBT plan we were receiving proper response till date, but after this enrollment , our QA did detail level testing for this plan and they observed that “LBT” plan has lots of customizations on Selerix portal ,which can result multiple scenarios , mentioning few below:
1)Employee can enroll for himself, Spouse and Child differently.
2)Spouse can enroll for herself, Employee and Child differently.

<Applications>

<Application>
<Coverage ProductID="13811">
<Tier>Employee Only</Tier>
<DeductionFrequency>26</DeductionFrequency>
<EmployeeCost>9.6200</EmployeeCost>
<PreTaxEmployeeCost>0.0000</PreTaxEmployeeCost>
<PostTaxEmployeeCost>9.6200</PostTaxEmployeeCost>
<EmployerCost>0.0000</EmployerCost>
<BenefitAmount>25000.0000</BenefitAmount>
</Coverage>
</Application>

<Application>
<Coverage ProductID="13811">
<Tier>Children Only</Tier>
<DeductionFrequency>26</DeductionFrequency>
<EmployeeCost>6.0000</EmployeeCost>
<PreTaxEmployeeCost>0.0000</PreTaxEmployeeCost>
<PostTaxEmployeeCost>6.0000</PostTaxEmployeeCost>
<EmployerCost>0.0000</EmployerCost>
<BenefitAmount>25000.0000</BenefitAmount>
</Coverage>
</Application>

<Application>
<Coverage ProductID="13811">
<Tier>Children Only</Tier>
<DeductionFrequency>26</DeductionFrequency>
<EmployeeCost>6.0000</EmployeeCost>
<PreTaxEmployeeCost>0.0000</PreTaxEmployeeCost>
<PostTaxEmployeeCost>6.0000</PostTaxEmployeeCost>
<EmployerCost>0.0000</EmployerCost>
<BenefitAmount>25000.0000</BenefitAmount>
</Coverage>
</Application>

</Applications>

Solution :
We should change our code such way that , read all <Application> nodes against single product(ProductID="13811"), and combine the cost of each and show it against employee cost in Workterra, but show Coverage’s for every individual (EE, SP, CH) separately. As Workterra System allows Separate Coverage’s for all enrolled entities(EE,SP,CH) in Single plan , but doesn’t allow to enter individual cost in single plan.